The present invention relates to a vane motor of the type including a rotor arranged in a housing and several cam rings disposed axially in side-by-side relation surrounding the rotor and having sets of vanes associated with one of the cam rings respectively, the vanes being slidable in radially extending slots in the rotor and dividing a working chamber located between the rotor and the cam rings and provided with inlet and outlet ports into and out from the working cells. The side plates laterally confine the working chamber.
A vane motor of this type is disclosed in the U.S. Pat. No. 3,455,245. That vane motor includes a housing wherein there are arranged axially in side-by-side relation two vane assemblies, each including of a cam ring, vanes, and a rotor element which are arranged between two side plates. The cam rings are of equal track and are disposed in axial alignment relative to their track. Bolts and dowels extending through the two cam rings prevent relative rotation of the cam rings and the two side plates. In a vane motor of such construction, the volumetric displacement of the motor can only be changed in steps by changing the number of vane assemblies arranged axially adjacent to each other.
Also, in the magazine "Olhydraulik und Pneumatik" 19 (1975) no. 3, pages 153 et sqq., a continuously adjustable double-action vane pump having only one cam ring which is rotatable relative to inlet and outlet ports for the purpose of changing the volumetric displacement is described.
Since this type of arrangement provides unfavorable flow conditions which may lead to high pressure pulsations, extensive measures are required to compensate for the detrimental effects on this pump.